(a) Field of the Invention
The present invention relates to a vertical alignment layer including a cyclic olefin copolymer. More specifically, the present invention relates to a vertical alignment layer capable of having alignment even in a low temperature process and exhibiting excellent liquid crystal vertical alignment by including a cyclic olefin copolymer having a specific substituent.
(b) Description of the Related Art
In accordance with the recent trend of increasing a size of display devices, applications of the large-sized display device are expanding to not only mobile devices such as a smart phone, laptop, etc., but also a large-wall mounted TV, etc. Therefore, the display devices are required to have high-definition, high quality, and a wide viewing angle, etc.
In particular, since a thin film transistor liquid crystal display device (TFT-LCD) which is driven by a thin film transistor is capable of independently driving individual pixels, a response speed of liquid crystal is significantly fast, and accordingly, it is possible to implement high-quality moving images, such that application ranges thereof have been gradually expanded.
In such a TFT-LCD, an alignment layer is used in a lower part of the liquid crystal layer so that a liquid crystal is usable as an optical switch, and the alignment layer includes an alignment copolymer, etc., to be applied to initial alignment of a liquid crystal molecule.
Here, the initial alignment refers to a mechanism in which a main chain of a copolymer is arranged in a predetermined direction, such that liquid crystal molecules are aligned in a state that voltage is not applied.
That is, in order that the liquid crystal is used as the optical switch in the TFT-LCD, the initial alignment of the liquid crystal in the predetermined direction needs to be induced on a layer in which a thin film transistor at the innermost of a display cell is formed. To this end, alignment layers including an alignment copolymer have been used.
Accordingly, in order to more effectively induce the initial alignment, the alignment copolymer included in the alignment layer needs to cause an interaction easily with molecules in the liquid crystal layer.
In general, for the liquid crystal alignment, there is a method of applying a polyamic acid heat resistant polymer onto a transparent glass and performing a heat treatment at a high temperature to form a polyimide polymer alignment layer.
However, since a polymer film substrate is used in the display device applied to a flexible display or a smart window, etc., the above-described method of applying the polyamic acid polymer onto the substrate and performing the heat treatment at a high temperature is not appropriate.
Therefore, a study on a vertical alignment layer capable of having alignment even in a low temperature process and exhibiting excellent liquid crystal alignment is demanded.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.